Elastic films are used in many applications such as in absorbent articles where strength and elasticity are needed. Ethylene plastomers are commonly used to produce elastic films. However, producing such ethylene-based elastic films is difficult, as the films can be tacky, can break easily during extrusion, and have limited elasticity. Polypropylene would be a better alternative in this regard, but low comonomer (less than about 8 wt % comonomer) polypropylene does not have the desired elasticity, and high comonomer polypropylene (greater than about 40 wt % comonomer, such as EP rubber) is not usable for conventional film extrusion as it needs to be crosslinked and would result in a film with a high level of gels, and also cannot be recycled. Other materials such as styrenic block copolymers and thermoplastic polyurethanes can be used to make elastic films; they offer excellent elasticity but they are relatively expensive and thus undesirable for products that are ultimately intended to be disposable.
It is known that certain polypropylene copolymers, having a mid-range of comonomer content (between about 5 to 25 wt % comonomer), a 0.5 to 40% level of crystallinity, and triad tacticity (of three propylene units) of 75% or greater have a desirable amount of elasticity as well as low cost. However, these propylene-α-olefins copolymers alone can be too tacky for practical use, and also lack bubble stability for making blown films. What would be desirable is a propylene-based composition suitable for making blown films having the advantageous low cost and elasticity of these propylene-based polymers, but also having improved bubble stability and lower level of tackiness. The inventor has found useful propylene-α-olefin compositions for such films.